pain under right shoulder blade

Hi I've been experiencing a sharp pain under my right shoulder for a couple of hours. It does not seem to be spreading and I've just taken a couple of regular strength aspirin. I'm not sure why I have this pain, I was on a conference call and noticed the pain after. I'm a little short of breath but can take deep (painless) breaths if I sit up straight. I tired to look up shoulder pain as it relates to heart attacks and found descriptions of pain in the center of the back and chest. I also laid down with a heating pad under my shoulder for about an hour... that didn't do anything. Should I be alarmed?